Hi everyone and welcome to a new tutorial on near-infrared spectroscopy for food analysis. Today we will show how to detect the difference between lactose-free milk and normal milk.
If you are interested in other tutorial on near-infrared spectroscopy for food analysis, feel free to check our posts on: macadamia
, and milk powder
Lactose intolerance and lactose-free milk Lactose
is a sugar naturally present in regular milk. Lactose intolerance
is the condition in which a subjects lacks the enzyme lactase
in the small intestine. The lactase is responsible for breaking down the lactose into its constituents glucose
That was a bit of a mouthful I know. Said in plain language, if we are lactose intolerant, our digestive system can’t process the milk sugar and that causes unpleasant symptoms as bloating, nausea, gas, etc.
Lactose intolerance is not an allergy (milk allergy
is a completely different thing) but can be relieved by avoiding the lactose. Dairy-free products do not contain lactose, but there are option such as lactose-free milk that are produced for lactose intolerants.
Lactose free milk is normally produced by ultra-pasteurization
of regular milk and by adding the lactase in it. The lactase breaks down the lactose to make the milk lactose-free.
Enters near-infrared spectroscopy
In this tutorial, we will show how we can detect the presence of milk in lactose-free milk or vice versa. In practice, everything else being equal, we are detecting the presence of lactase (+ glucose and galactose) in lactose-free milk, as opposed to the presence of lactose in regular milk.
We prepared different samples starting with 100% milk, and changing the ratio of milk/lactose-free in ⅛ intervals. That means the first sample was ⅛ milk and ⅞ lactose-free milk, the second sample was 2/8 milk and 6/8 lactose-free milk, and so on.
We used our Brimrose Luminar 5030 AOTF-NIR spectrometer, mounted on a vertical bracket to scan the samples. We took good care to keep the distance of the spectrometer from the surface of the milk samples to be always the same. In this way we minimised sample-to-sample variations.